Correlation between anode manufacturing process and anode reactivity for CHALCO plant in Guizhou, China

L'aluminium est produit via Pélectrolyse et les anodes utilisées dans ce procédé sont fabriquées du carbone. La basse consommation du carbone (anode) est importante pour l'industrie de l'aluminium parce qu'elle affecte directement le coût de production aussi bien que les émissions environnementales. La consommation des anodes est fortement influencée par ses propriétés. Dans l'électrolyse d'aluminium, l'étude de la fabrication des anodes et l'amélioration de la technique de sa production permettront l'économie en énergie et la réduction des émissions gazeuses pour l'industrie d'aluminium. Les réactivités à CO2 et à l'air et la perméabilité à l'air sont des indices importants pour l'évaluation des anodes en carbone parce que non seulement elles sont liées à la densité de ces dernières mais aussi à leur consommation, et cela permettra la détermination des potentiels pour l'économie en énergie et la réduction des émissions de CO2 et de gaz nocifs durant la production des anodes en carbone. L'objectif global du projet est d'améliorer la qualité des anodes présentement utilisées. Premièrement, une enquête du procédé à l'usine à été effectuée pour identifier les parties problématiques. Des petits échantillons des anodes ont été préparés à partir des matières premières disponibles à la province de Guizhou de la Chine. Des différentes formulations des anodes ont été essayées. Parmi toutes les formulations, la meilleure a été choisie en comparant leurs propriétés (la perméabilité à l'air, les réactivités à l'air et à CO2). Les microstructures des cokes et des anodes et le comportement de la pénétration du brai ont été analysés avec MEB. Les échantillons, préparés suivant des formulations pré11 déterminées, ont été cuits dans un analyseur thermogravimétrique (TGA). L'analyse des volatiles a aussi été effectuée en utilisant un cromotographe à gaz (GC) couplé avec le TGA. A partir de ces données, les paramètres du model cinétique de la dévolatilisation, développé antérieurement à l'UQAC, ont été déterminés. Les propriétés des anodes (les réactivités à CO2 et à l'air et la perméabilité à l'air) cuites dans TGA aussi bien que celles cuites à l'usine ont été mesurées. La qualité des anodes a été corrélée avec les propriétés des matières premières et les conditions de la préparation de la pâte et de la cuisson des anodes. - Aluminum is produced by electrolysis, and the anodes used for this process are made of carbon. Low carbon (anode) consumption is important for the aluminum industry because it directly affects the cost of production as well as environmental emissions. The anode consumption is strongly influenced by the properties of anode. In aluminum electrolysis, the study of carbon anode manufacturing and the improvement of its production techniques lead to savings in energy and reduction in gaseous emissions for the aluminum company. The CO2 and air reactivities and air permeability are important indices to evaluate carbon anodes because they relate not only to anode density but also to anode consumption, which will help assess the potential for saving energy and reducing CO2 and hazardous gas emissions of the carbon anode production process. The global objective of the project is to improve the quality of the presently used carbon anodes. First a plant process review was conducted to identify the problem areas. Small anode samples were prepared from the raw materials available in the Guizhou province of China. Different anode formulations were tried. The best one among them was chosen based on the anode properties (air permeability, air and CO2 reactivities) obtained. The microstructures of cokes and anodes and the pitch penetration behavior were analyzed using SEM. The anode samples prepared with pre-determined formulation were baked in a thermogravimetric analyzer (TGA). The volatile analysis was carried out using a gas chromatograph (GC) coupled with the TGA. From these data, the parameters of the kinetic model of the devolatilization developed previously at UQAC were determined. The properties of anodes (CO2 reactivity, air reactivity, and air permeability) baked in the TGA were also measured. Anode quality (properties) was correlated with the properties of raw materials as well as paste preparation and anode baking conditions

Study on high-purity alumina preparation and its applications

Wastewater from different aluminum processing plants contains different surface treatment liquids. These liquids are strictly prohibited from being discharged directly into the environment due to their high acidity. Different factories and enterprises add water to dilute them or neutralize them with alkali. These approaches not only cause a part of the aluminum ions being discharged, but also result in the release of a large number of harmful metal ions and heavy metal ions. In such cases, a large amount of water and alkali are consumed; at the same time, surface water, groundwater and soil become polluted by a large volume of wastewater and different metal ions. The main objectives of the project are: 1) to extract ultra-pure aluminum ions from wastewater and to study the effect of different parameters on the efficiency of the process; 2) to produce ultra-pure nano-alumina from wastewater using an organic template and to study the effect of different parameters on the particle size distribution as well as on the morphology of the nanoparticles; 3) to explore the possibility of different applications for different types of alumina particles. In this work, aluminum was extracted from the wastewater in the form of alum. This aluminum alum solution was later used to produce 99.999% pure (5N) nano-alumina particles. Two different methods, namely single and double template methods, were used to control the size and the nature of the alumina particles. A single template method was used to produce 99.999% pure (5N) spherical alumina nanoparticles. The aluminum alum solution was hydrolyzed to produce boehmite which was used to produce the spherical alumina nanoparticles. Gum arabic and urea were used to produce the single template. These alumina nanoparticles were converted to alpha (α) form by heating. Then, the α-alumina particles were used to produce sapphire crystals. An evaporation-induced synthesis approach with double template was used to produce spherical mesoporous nanoparticles of uniform size distribution. These particles were used for the photoacoustic tomography. The originality of the project lies in the utilization of new sources of raw materials (wastewater from industries) and using chelating polymers as well as additives to develop a novel and environment friendly high purity alumina (HPA) production method. In addition, the alumina particle size and its distribution are controlled precisely, which is difficult to achieve with other alumina production methods. Les eaux usées provenant des différentes usines de traitement de l'aluminium contiennent de différents liquides de traitement de surface. Ces liquides sont strictement interdits d'être déchargés directement à l'environnement en raison de leur forte acidité. Des différentes usines et entreprises ajoutent de l'eau pour les diluer ou les neutralisent avec l'alcali. Ces traitements provoquent non seulement la décharge d'une partie des ions d'aluminium, mais également la libération d'un grand nombre d'ions métalliques nocifs et d'ions de métaux lourds. Dans ces cas, des grandes quantités de l'eau et de l'alcali sont consommées; en même temps, les eaux de surface, les eaux souterraines et le sol sont pollués par un grand volume d'eaux usées et de différents ions métalliques. Les objectifs principaux du projet sont : 1) d'extraire les ions d’aluminium ultra-purs des eaux usées et d'étudier l'effet de différents paramètres sur l'efficacité du procédé; 2) de produire la nano-alumine ultra-pure à partir des eaux usées en utilisant un modèle organique et d’étudier l'effet de différents paramètres sur la distribution granulométrique et la morphologie des nanoparticules; 3) d’explorer différentes applications des différents types des particules d'alumine. Dans ce travail, l'aluminium a été extrait des eaux usées sous forme d'alun en utilisant un modèle simple. Cette solution d'alun a ensuite été utilisée pour produire des particules de nano-alumine pur à 99,999% (5N). La solution d'alun a été hydrolysée pour produire une bohémite qui a également été utilisée pour produire des nanoparticules d’alumine sphérique pure à 99,999% (5N). Ces microparticules d'alumine ont été utilisées pour produire des cristaux de saphir. Une approche basée sur la séparation induite par évaporation à double modèle a été utilisée pour produire des nanoparticules mésoporeuses sphériques avec une distribution de taille uniforme. Ces particules ont été utilisées pour la tomographie photoacoustique. L’originalité du projet est l’utilisation de nouvelles sources des matières premières (l’eau usée des industries) et des polymères chélatants et des additives afin de développer une nouvelle méthode écologique pour la production de l’alumine de haute pureté. De plus, la taille des particules de l’alumine et sa granulométrie sont contrôlées précisément, ce qui est difficile à atteindre avec d’autres méthodes de la production de l’alumine

Correlation between anode recipe and anode properties

The variation of anode raw material quality is becoming more and more challenging for the industry. Therefore, the anode recipe should be adjusted according to the available anode raw material in such a way that the quality of the anode remains consistent. The CO2 and air reactivities as well as air permeability are important indices to evaluate carbon anodes because they relate not only to anode density but also to anode consumption, which can help assess the anode performance. This paper presents the anode formulation tests carried out together with SEM image analysis with the objective of decreasing the anode reactivities and air permeability by optimizing the anode recipe

The effect of novel synthetic methods and parameters control on morphology of nano-alumina particles

Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation

Novel method for extracting ultra high purity alumina from wastewater

An object of the present invention is to provide a novel method for extracting ultra high purity alumina from wastewater. Wastewater is recycled, filtered, concentrated and pretreated in order to mix with alkali solution and extraction agent PX-17, undergoing 2 times of purification, adding control agent SX-1 and high temperature heat treatment to finally obtain ultra high purity nano-alumina particles which purity reaches as 99.999% and particle size reaches as 20-200 nm

Review of research on template methods in preparation of nanomaterials

The nanomaterials have been widely used in various fields, such as photonics, catalysis, and adsorption, because of their unique physical and chemical properties. Therefore, their production methods are of utmost importance. Compared with traditional synthetic methods, the template method can effectively control the morphology, particle size, and structure during the preparation of nanomaterials, which is an effective method for their synthesis. The key for the template method is to choose different templates, which are divided into hard template and soft template according to their different structures. In this paper, the effects of different types of templates on the morphology of nanomaterials during their preparation are investigated from two aspects: hard template and soft template, combined with the mechanism of action

Alloying Iron into Palladium Nanoparticles for an Efficient Catalyst in Acetylene Dicarbonylation

Motivated by the prominent catalytic performance and durability of nanoalloy catalysts, the Pd-based bimetallic nanoalloy catalysts were prepared using an aqueous reduction method. The Fe-Pd bimetallic nanoalloy catalyst (nano-Fe/Pd) demonstrated 98.4% yield and 99.7% selectivity for the unsaturated 1,4-dicarboxylic acid diesters. Moreover, the inductively coupled plasma (ICP) analysis shows that the Pd leaching of the catalyst can be effectively suppressed by alloying Fe atoms into the Pd crystal lattice for acetylene dicarbonylation. The detailed catalyst structure and morphology characterization demonstrate that introducing Fe into the Pd nanoparticles tunes the electronic–geometrical properties of the catalyst. Theoretical calculations indicate that the electrons of Fe transfer to Pd in the nano-Fe/Pd catalyst, enhancing activation of the C≡C bond in acetylene and weakening CO absorption capacity on catalyst surfaces. Alloying Fe into the Pd nanocatalyst effectively inhibits active metal leaching and improves catalyst activity and stability under high-pressure CO reactions

Thermogravimetric study on devolatilization kinetics of Chinalco anodes during baking

The production of aluminum requires the use of carbon anodes which are manufactured from coke, pitch, and recycled butts and anodes. Pitch acts as a binder. Green anodes are produced by mixing all these ingredients and then forming them in a compactor. The final step is the baking of green anodes, which determines the final anode properties. During baking, volatiles evolve from the pitch which carbonizes and binds the particulate matter. Anode quality greatly influences the performance of electrolytic cells and has an impact on carbon consumption, energy use, green house gas emissions, and cost. In this project, the effects of the baking conditions on some of the anode properties (air permeability, air and CO2 reactivities) were studied, and the devolatilization kinetics was determined for different cases. The results indicate that the lower heating rates and higher baking temperatures improve the above properties. In this article, the experimental work and the methodology for the determination of the kinetic expressions for devolatilization are described, and the results are presented. The position of volatile evolution in the baking furnace can be determined via these expressions, and this could be effectively used in controlling the volatile combustion to improve the furnace performance

A Ratiometric Fluorescent Sensor for Cd2+ Based on Internal Charge Transfer

This work reports on a novel fluorescent sensor 1 for Cd2+ ion based on the fluorophore of tetramethyl substituted bis(difluoroboron)-1,2-bis[(1H-pyrrol-2-yl)methylene]hydrazine (Me4BOPHY), which is modified with an electron donor moiety of N,N-bis(pyridin-2-ylmethyl)benzenamine. Sensor 1 has absorption and emission in visible region, at 550 nm and 675 nm, respectively. The long wavelength spectral response makes it easier to fabricate the fluorescence detector. The sensor mechanism is based on the tunable internal charge transfer (ICT) transition of molecule 1. Binding of Cd2+ ion quenches the ICT transition, but turns on the π − π transition of the fluorophore, thus enabling ratiometric fluorescence sensing. The limit of detection (LOD) was projected down to 0.77 ppb, which is far below the safety value (3 ppb) set for drinking water by World Health Organization. The sensor also demonstrates a high selectivity towards Cd2+ in comparison to other interferent metal ions

Phosphorus-Doped Graphene Electrocatalysts for Oxygen Reduction Reaction

Developing cheap and earth-abundant electrocatalysts with high activity and stability for oxygen reduction reactions (ORRs) is highly desired for the commercial implementation of fuel cells and metal-air batteries. Tremendous efforts have been made on doped-graphene catalysts. However, the progress of phosphorus-doped graphene (P-graphene) for ORRs has rarely been summarized until now. This review focuses on the recent development of P-graphene-based materials, including the various synthesis methods, ORR performance, and ORR mechanism. The applications of single phosphorus atom-doped graphene, phosphorus, nitrogen-codoped graphene (P, N-graphene), as well as phosphorus, multi-atoms codoped graphene (P, X-graphene) as catalysts, supporting materials, and coating materials for ORR are discussed thoroughly. Additionally, the current issues and perspectives for the development of P-graphene materials are proposed